The rise of the Internet has enabled access to a wide variety of content items, e.g., video and/or audio files, web pages for particular subjects, news articles, etc. Such access to these content items has likewise enabled opportunities for targeted advertising. For example, content items of particular interest to a user can be identified by a search engine in response to a user query. The query can include one or more search terms, and the search engine can identify and, optionally, rank the content items based on the search terms in the query and present the content items to the user (e.g., according to the rank). This query can also be an indicator of the type of information of interest to the user. By comparing the user query to a list of keywords specified by an advertiser, it is possible to provide targeted advertisements to the user.
Another form of online advertising is advertisement syndication, which allows advertisers to extend their marketing reach by distributing advertisements to additional partners. For example, third party online publishers can place an advertiser's text or image advertisements on web pages that have content related to the advertisement. Because the users are likely interested in the particular content on the publisher webpage, they are also likely to be interested in the product or service featured in the advertisement. Accordingly, such targeted advertisement placement can help drive online customers to the advertiser's website.
Advertisers can bid for placements based upon how much the advertiser values the placement. In some examples, the advertiser can bid based upon impressions of the advertisement. In such examples, the advertiser is charged whenever the advertisement is served. In other examples, the advertise can bid based upon a click-through for the advertisement. In such examples, the advertiser is charged only when a user clicks on the advertisement after the advertisement is served to the user.